Polyester-imide wire coatings thinned in conventional cresylic acid/aromatic hydrocarbon solvent blends have been used commercially for a number of years. Taking the base polymer one can solubilize it in water along with an amine. In attempting to use the same curatives as are employed in the non-aqueous or organic solvent system previously mentioned it was soon discovered that they were insoluble in water. This necessitated a search for crosslinkers that were soluble in water, and those were mainly organic titanates, such as Tyzor TE and LA which are titanium chelates of triethanolamine and the ammonium lactate salt, respectively.
Following the teachings of Meyer et al in U.S. Pat. No. 3,426,098, (the entire disclosure of which is hereby incorporated by reference and relied upon) if one were to take any of the polyester-imide base polymers and solubilize it with distilled water, an amine, a polar solvent and modify it with Tyzor TE, the baked enamel on copper wire would be out-of-round or eccentric, grainy or rough because of poor flow in the wire tower during the baking or curing operation. Extensive wire tower runs with another standard polyester-imide base having a fixed diimidediacid molar content in relation to the terephthalic acid molar content present all ran with an appearance rating of five (5) with or without a heavy grain and/or rough or blistery.
The present invention relates to novel polyester-imides and wire enamels prepared therefrom that are truly water-soluble, transparent, and truly clear in appearance.
It is an object of the present invention to prepare novel polyester-imides.
Another object is to prepare novel wire enamels containing polyester polyimides that are not only watersoluble, but soluble in the conventional cresylic acid/aromatic hydrocarbon blends and in each case perform equally as well.
An additional object is to prepare electrical conductors having improved high temperature resistant coatings.
A further object is to prepare wire enamels having unusually good flexibility aging and heat shocks as compared to presently available polyester wire enamels.
Another object of this invention is to prepare heat-resistant wire enamels that have good heat shocks at 200.degree. C. without the use of a topcoat, such as polyethylene terephthalate, nylon, or an amide-imide polymer.